This invention relates to a magnetic head in which a pair of magnetic core halves, each having a winding groove in which a coil is wound, are abutted and unified together via thin magnetic metal films and in which a magnetic gap is defined between the abutting surfaces of the core halves. More particularly, it relates to a magnetic head having a structure for prohibiting peeling of the thin magnetic metal films.
In a magnetic recording/reproducing apparatus, such as a video tape recorder (VTR) or a digital audio tape recorder (R-DAT), investigations for reducing the recording wavelength of information signals are proceeding with a view to improving the picture quality. In keeping up therewith, a high-coercivity magnetic recording medium, such as a so-called metal tape employing magnetic metal powders as magnetic powders or an evaporation tape having a magnetic metal material directly deposited on a base film, has come into use.
Investigations are also being conducted in the field of the magnetic heads in connection with development of the high-coercivity magnetic recording medium. Thus, for coping with the high-coercivity magnetic recording medium, a magnetic head has been developed in which a magnetic metal material is used as a core material and the track width is reduced.
Such magnetic head is shown in FIG. 1, in which abutment surfaces of a pair of magnetic cope halves 101, 102, formed of magnetic oxides, such as Mn-Zn ferrite, are partially removed for forming surfaces for forming thin magnetic metal films, and thin magnetic metal films 105, 106, formed e.g., of sendust, are formed on these forming surfaces by the vacuum thin film forming technique. These thin magnetic metal films 105, 106 are abutted to each other for forming a magnetic gap 107. A slide contact surface for a magnetic tape is formed in a track width control groove and a low-melting glass or high-melting glass 108 is charged in the track width control groove for prohibiting abrasion of the thin magnetic metal films 105, 106.
On the abutting surfaces of the magnetic core halves 101, 102, there is formed a winding slot 109 for placing a coil therein and for controlling the depth d of a magnetic gap 107. The winding slot 109 is comprised of an upper inclined portion 109a for controlling the depth d of the magnetic gap 107 and a bottom 109b having a value of Rmax approximately 0.2 .mu.m by toughening. The winding slot 109 encompasses not only the sole window type in which the slot is formed in only one of the magnetic core halves but also the dual window type in which the slot is formed in each of the magnetic core halves 101, 102.
For producing this sort of the magnetic head, a pair of core blocks are fabricated through a process including a step of forming grooves in a substrate of a magnetic oxide and forming a thin magnetic metal film, a step of charging fused glass 108 and machining the surface to a mirror finish. These core blocks are abutted together to form a unified block which is sliced into magnetic head chips and a coil is placed in each of the magnetic chips.
In abutting the magnetic core halves, on each of which a thin magnetic metal film is formed, for unifying these core halves, there is produced a force of stress at the time of forming these films 105, 106 and thermal stress induced when charging the fused glass in the track width control groove thus lowering adhesion in an interface between the films 105, 106 and the ferrite. The result is that the thin magnetic metal film tends to be peeled during the subsequent step of chip slicing and coil winding.
For overcoming this inconvenience, it may be contemplated to use specific shapes of the inclined section 109a of the winding slot 109 controlling the depth of the magnetic gap 107, or to charge the fused glass as far as a winding section 109c of the winding slot 109, as shown in FIG. 2. However, this may lead to difficulties in placing the coil in the slot in the subsequent coil winding step.